The invention is based on an apparatus for regulating the pressure in a hydraulic circuit. Apparatuses of this type are used in automatic gearboxes of motor vehicles in particular, to trigger gear changes via control of the pressure level, for example.
For this, known apparatuses comprise an electrically triggerable pressure-control valve, like the one made known previously in DE 197 33 660 A, for example. This pressure-control valve comprises a solenoid part constructed in conventional fashion having coil, coil core, flux concentrating element and armature, and a hydraulic part having mechanical linkage with the solenoid part. In the hydraulic part, a shutoff element able to be acted upon by the armature controls the flow of hydraulic fluid between inlet passages, working passages, and return passages.
This known pressure-control valve can be installed with its hydraulic part in a receptacle devicexe2x80x94a xe2x80x9chydraulic control blockxe2x80x9dxe2x80x94in which recesses are provided that direct hydraulic fluid and are matched to the corresponding passages of the pressure-control valve. Appropriate devices are provided to dampen pressure pulsations, which can occur during operation of the pressure-control valve in the recess matched to the working passage. These devices are attached in the receptacle device as separate components.
The separate arrangement of the damping devices described is disadvantageous, because it makes a large number of holding elements necessary, takes up a relatively large space, generates additional work, and is costly to install.
In contrast, an apparatus according to the invention for controlling the pressure in a hydraulic circuit has the advantage that the means for damping pressure pulsations are an integral component of the pressure-control valve. This saves space, simplies the manufacture of the receptacle device, and makes separate holding elements superfluous, without making assembly of the pressure-control valve itself more difficult. The pressure pulsations are damped by means of the invention directly at the site of origin, which greatly improves the damping effect. Due to the damping, the pressure/flow characteristic of a pressure-control valve can be kept within narrow tolerances under nearly all operating conditions. Additionally, the prevention of pressure pulsations has a positive effect on the wearing behavior of the pressure-control valve, so that its service life is extended.
The devices can be integrally molded on one of the sealing elements of the pressure-control valve particularly easily, so that the total number of components to be obstructed remains unchanged. The devices, together with the housing of the pressure-control valve, enclose a damping chamber having a variable volume. Its damping behavior can be varied by means of vents to the recess of the receptacle device matched to the return passage of the pressure-control valve in accordance with the specific case of application. This vent can also be designed in advantageous fashion as throttling point.